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Aspect Ratio Calculator — 16:9, 4:3, 1:1 & Custom

Resize an image or video while keeping the aspect ratio. Type either width or height — the other fills automatically.

Original

Aspect ratio: 16:9

New size (preserves ratio)

Type either dimension — the other fills automatically.

16:9

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About this tool

Calculate any aspect ratio — 16:9, 4:3, 1:1, 21:9 and custom

Enter a width or a height and lock a ratio — the other dimension fills in automatically, so you get exact pixel sizes without doing the math by hand. Works for the common presets (16:9 widescreen, 4:3, 1:1 square, 9:16 vertical, 21:9 ultrawide, 3:2 photo) or any custom ratio you type.

Common 16:9 resolutions

  • 1920 × 1080 — 1080p Full HD
  • 1280 × 720 — 720p HD
  • 2560 × 1440 — 1440p QHD
  • 3840 × 2160 — 4K UHD

How to calculate an aspect ratio

Divide width by height and simplify: 1920 ÷ 1080 = 1.777…, which is 16:9. To resize while keeping the ratio, multiply both sides by the same factor — halving 1920 × 1080 gives 960 × 540, still 16:9. This calculator does that instantly so images and video never end up stretched or squished.

Resize or crop a photo to a ratio

Use it to find the target pixel size before cropping a picture to 1:1 for an Instagram post, 16:9 for a YouTube thumbnail, or 9:16 for Reels and Stories. Everything runs in your browser — nothing is uploaded.

How to use the Aspect Ratio Calculator

Takes about a minute. No signup, no download, your data stays in your browser.

  1. 1
    Open the tool. Scroll up to the Aspect Ratio Calculator above — it loads instantly in your browser, no install needed.
  2. 2
    Enter your values. The fields come pre-filled with realistic defaults so you can see how it works — replace them with your own numbers.
  3. 3
    Read the result. The output updates instantly. Copy or share it — nothing is uploaded to a server, everything stays on your device.

Frequently asked questions

Common questions about the Aspect Ratio Calculator.

Is the Aspect Ratio Calculator free to use?

Yes. The Aspect Ratio Calculator on 7BusyBoss is completely free — no signup, no paywall, no usage cap. We do recommend paid alternatives in a sidebar card, but the core tool stays free.

Do I need to sign up to use the Aspect Ratio Calculator?

No. The Aspect Ratio Calculator works instantly in your browser — no account needed. Signing in with Google is optional and only unlocks features like saving favorites and higher AI build limits.

Does the Aspect Ratio Calculator work on mobile?

Yes. Every tool on 7BusyBoss is mobile-responsive and works in any modern browser — Chrome, Safari, Firefox, Edge — on phones, tablets and desktops.

Is my data safe when I use the Aspect Ratio Calculator?

Yes. The Aspect Ratio Calculator runs entirely in your browser — your inputs never leave your device unless the tool explicitly fetches public data (e.g. currency rates). We don't store the values you type.

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